The present invention relates to remote convenience systems, and is particularly directed to systems that include an adjustable pulse detection receiver.
Remote convenience systems are known in the art. Such remote convenience systems permit remote control of certain functions. One example type of a remote convenience system is for remotely controlling vehicle functions. Other example types of remote convenience systems include garage door opener systems and entry light activation systems. Focusing on the remote convenience vehicle systems, remotely controlled vehicle functions include locking and unlocking functions of one or more vehicle doors. A remote convenience system that permits remote locking and unlocking is commonly referred to as a remote keyless entry system. Such remote convenience vehicle systems may provide for control of other vehicle functions. For example, a remote vehicle locator function may be provided. The vehicle locator function causes a horn to emit a horn chirp and/or the headlights of the vehicle to flash xe2x80x9cONxe2x80x9d. This allows a person to quickly locate their car within a crowded parking lot.
Known remote convenience vehicle systems include a receiver/controller unit mounted in an associated vehicle and at least one portable hand-held transmitter unit located remote from the receiver/controller unit. Each transmitter unit is provided with one or more manually actuatable switches. Each switch is associated with a vehicle control function to be performed. The transmitter unit includes circuitry that responds to the actuation of one of the switches to transmit a function request message, along with a security code, in the form of a digital signal. A signal that is received by the receiver/controller unit is processed such that the vehicle performs the requested function.
The remote convenience systems operate in the ultrahigh frequency (UHF) portion of the radio frequency (RF) spectrum. Specifically, the signals from the transmitter units are in the UHF portion of the spectrum that is allocated by the United States Federal Communications Commission (FCC) for unlicensed transmission devices. FCC regulations stipulate that such unlicensed devices cannot have a transmitted signal strength that exceeds a preset maximum. Some countries other than the United States only permit very low levels of transmitted power. The transmitted power level in these countries is lower than the permitted level in the United States. For example, in Japan, remote convenience transmitter units have typical transmission power levels 30 dB below that of a typical United States remote convenience transmitter unit. In addition, within the United States, FCC regulations stipulate that the unlicensed devices must not cause undo radio interference and must operate despite the presence of any radio interference.
Often, it is desirable to accomplish remote control performance of certain functions at a longest possible distance. One example of such a function that is performed at the longest possible distance is the remote vehicle locator function. To illustrate such a scenario, consider a shopping mall patron exiting a shopping mall building and being faced with the task of visually locating their car within a vast shopping mall parking lot. It will be beneficial to be able to actuate the remote vehicle locator function from a location near the exit door of the shopping mall, before proceeding into the parking lot.
In order for a receiver/controller unit located within the associated vehicle to receive a low power signal, the receiver/controller unit must have a high sensitivity and must have a high ability to differentiate the signal from any noise.
Another issue which presents itself for remote convenience systems is that the type of the circuitry hardware that is used within the receiver/controller unit is often dependent upon the type of signal that is transmitted from the associated transmitter unit. Specifically, if the transmitted signal contains a pulse string that has a duty cycle that is approximately fifty percent, the receiver/controller unit typically includes an average detector for discriminating pulses within the transmitted signal. A threshold level, used to determine the occurrence of pulses, is set at an average signal level.
However, if the transmitted signal contains a pulse string that has a duty cycle that is much lower than fifty percent, the receiver/controller unit typically requires the use of a peak detector to discriminate the occurrence of pulses within the transmitted signal. A threshold level is set at some percentage of a peak value of the signal.
It is to be appreciated that an average detector does not perform well for low duty cycle signals and the peak detector does not perform well for high duty cycle signals. Thus, different hardware setups must be provided in the receiver/controller units, dependent upon the type of transmitted signal.
In accordance with one aspect, the present invention provides a receiver/controller apparatus for receiving an electromagnetic signal comprised of a plurality of pulses that convey a remote convenience function request, and for causing performance of the requested function. A comparator of the apparatus has a first input for receiving an electrical signal with an electrical characteristic that varies to convey the remote convenience function request. A second input of the comparator receives a threshold electrical characteristic value. An output of the comparator provides a signal that is indicative of the occurrence of the electrical characteristic of the electrical signal exceeding the threshold value and that conveys the remote convenience function request. The apparatus includes means for adjusting the threshold electrical characteristic value.
In accordance with another aspect, the present invention provides a receiver/controller apparatus for a remote convenience system. The apparatus is responsive to a remote convenience function request conveyed via an electromagnetic signal transmitted from a portable transmitter for controlling performance of an associated function. Antenna means picks-up the electromagnetic signal and outputs a respective, electrical antenna-output signal conveying the function request. Receive circuitry means of the apparatus processes the antenna-output signal and outputs an electrical signal that conveys the function request in response to the processing of the antenna-output signal. The receive circuitry means includes a comparator that has a first input for receiving an electrical signal with a voltage that varies to convey the remote convenience function request. A second input of the comparator receives a threshold voltage value. An output of the comparator provides a signal indicative of the occurrence of the voltage of the electrical signal exceeding the threshold voltage value. The receive circuitry means includes means for adjusting the threshold voltage value.
In accordance with another aspect, the present invention provides a method of receiving an electromagnetic signal comprised of a plurality of pulses that convey a remote convenience function request, and for causing performance of the requested function. The electromagnetic signal is picked-up. An electrical antenna-output signal conveying the function request is output. A first signal with a voltage is derived from the antenna-output signal. The voltage of the first signal varies to convey the remote convenience function request. A second signal that has a threshold voltage value is provided. The first and second signals are compared. An output signal that indicates the occurrence of the voltage of the first signal exceeding the threshold voltage value is provided to convey the function request. The threshold voltage value of the second signal is adjusted.